<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        .box1 {
            height: 500px;
            border: 10px solid red;
            margin: 0px 200px;
            /* 200+10+0+auto+0+10+200 = 1500 */
        }

        .box2 {}
    </style>
</head>

<body>
    <div class="box1">
        <div class="box2">

        </div>
    </div>
</body>

</html>